Slack eliminating device for sheetfeeding apparatus



Oct. 7, 1969 J. o. ROBERTSON SLACK ELIMINATING DEVICE FOR SHEET-FEEDING APPARATUS Filed Sept. 29, 1966 3 Sheets-Sheet 1 m I mm m -v d if: Q\ 6m ow 4 ov 4| N INVENTOR JOHN D. ROBERTSON MM mm ATTORNEYS Oct. 7, 1969 J. o. ROBERTSON SLA K ELIMINATING DEVICE FOR SHEET-FEEDING APPARATUS Filed Sept. 29. 1966 3 Sheets-Sheet 2 FIG. 3

N w m. TR N E 8 0 R D N H 0 J ATTORN EYS 1969 J. D. ROBERTSON 3, 7 9

SLACK ELIMINATING DEVICE FOR SHEET-FEEDING APPARATUS Filed Sept. 29, 1966 5 Sheets-Sheet I0 I P A FIG. 7 [8 I 72? 24 I8 L 1&3- ffvimi FIG. 8

IN VENTOR.

JOHN D. ROBERTSON BY ATTORNEYS United States Patent 3,470,5i92 SLACK ELEMINATING DEVICE FOR SHEET- FEEDING APPARATIE .lohn D. Robertson, Tauntou, Mass, assignor to Mount Hope Machinery (Zompany, Tauntou, Mass, a corporation of Massachusetts Filed Sept. 29, I966, Ser. No. 582,919 Int. Cl. D06c 3/06; B65h 25/26, 17/22 US. Cl. 26--63 9 Claims ABSTRACT OF THE DISCLUSURE The invention is a curved roll and mounting means therefor, for automatically removing slack from a travelling web of material. Each end of the roll axle is mounted in first bearings so as to be rotatable about a straight axis intersecting the curved axle of the roll, with each of the first bearings also being independently mounted by means of second bearings so as to be movable in a direction having a component perpendicular to the direction of travel of the sheet.

This invention relates to an improved device for eliminating slack in sheets travelling longitudinally through sheet feeding apparatus. In many processes for treating running lengths of paper, textiles, and other sheet or web materials, differential tension or differential shrinkage causes the sheet to become slack at either or both edges, or in the center. This causes various problems, as related to the particular process in question; wrinkles occur, which may result in creases when winding, uneven application of material when coating, and irregularly cut edges when shearing.

It has previously been proposed to mount the ends of a straight roll on independently pivoted arms, and to bias the roll resiliently into a travelling sheet in an effort to obtain uniform tautness and eliminate slack regions. The straight roll may be followed, in the downstream direction of sheet travel, by one or more expander rolls mounted on fixed axes, to spread the sheet laterally and thus draw out wrinkles, This solution is not highly effective unless the slack condition increases rather uniformly from one edge to the other, which is often not the case.

It is the primary object of the present invention to provide an improved slack eliminator which is more ef fective to eliminate slack from any local region across the width of a traveling sheet. Further objects and advantages will become apparent as the following description proceeds.

Briefly stated, I provide a curved roll which is rotatable about a normally-stationary longitudinally-curved axle; the axle is mounted in support means which permit angular displacement about a longitudinal rectilinear axis, for turning the convex face of the roll more or less into a sheet travelling over the roll. The support means also allow the axle to tilt endwise; in one form, they comprise arm means pivotally mounted for independent movement of the opposite ends of the axle about an axis parallel to but offset from the roll. In another form, the ends of the axle are simply supported for sliding movement in slots of a frame, as described below. The roll is biased into the sheet, by gravity or otherwise.

A difference in tension as between the opposite edges of the sheet, as when one edge is slack, causes the axle to tilt end-wise in a manner to eliminate the slackness of the loose edge. To this extent, the action is similar to that of prior devices previously described.

However, if relative slackness occurs as between the center and the edges of the sheet, the reaction moments 3,470,592 Patented Oct. 7, 1969 of the sheet acting on the roll about the rectilinear axis become unbalanced, and the axle will be turned to a position which corrects the slack condition; that is, the convex face of the roll will turn into or out of the center of the web in a manner to equalize roll contact between the center and edges of the sheet.

It is preferred that the rectilinear axis of axle support pass substantially through the center of gravity of the roll, so that the axle may turn freely to vary the convexity of the roll surface portion engaging the sheet. Since a certain amount of torque must be applied by the travelling sheet to rotate the roll continuously about its curved axle, it is also desirable to provide counterweighting means on the axle to balance this torque. In the absence of counterweighting, the applied torque would tend to rotate the convex face of the roll out of the sheet, which would cause the edges to become tighter than the center. Indeed, in working with very stretchy sheet material, or with low sheet tension, a counterweight may be necessary to prevent continuous rotation of the axle.

It is also desirable, though not necessary in all cases, to partially counterbalance the gravitational or other bias of the roll into the sheet, by means of springs, counterweights, pneumatic cylinders or the like. These counterbalancing means may be adjustable, so that for a given level of sheet tension, the roll will deflect the sheet to the extent necessary to produce a desirable wrap angle. As is well known in the art, the most desirable wrap angle depends on the amount of lateral expansion or wrinkle removal required.

While the specification concludes with claims particularly pointing out the subject matter which I regard as my invention, it is believed that a clearer understanding may be gained from the following detailed description of a preferred embodiment thereof, with reference to the appended drawings, in which:

FIGURE 1 is a fragmentary plan view, partially in section, of a preferred embodiment of the improved slack eliminator;

FIGURE 2 is a fragmentary sectional view taken along line 2--2 in FIGURE 1, looking in the direction of the EU'I'OWS;

FIGURES 3-6 are schematic views looking from an end of the curved roll, showing it in various operative positions;

FIG. 7 is a plan view of an end portion of an alternate embodiment; and

FIG. 8 is an and elevation of the FIG. 7 embodiment.

A curved roll 10 of conventional construction is provided, having a flexible sleeve 12 of elastomeric material received circumferentially about an axially-spaced series of spools 14; the spools are in turn mounted upon a series of bearings 16 for rotation about a longitudinally-curved axle 18. Rolls of this type are well known in the art, and are widely used for lateral expansion or contraction of sheet or web materials, for correction of weft distortions in woven materials, and for other purposes.

The ends of the axle 18 are secured in angularly-adjusted relation within split clamping blocks 20 by means of set screws 22, and the clamping blocks extend into a pair of stub shafts 24 which are aligned on a rectilinear axis A. The elements 18, 20, and 24 combine to form axle means for the roll. The axis A preferably passes substantially through the center of gravity CG. of the roll, so that the roll and axle means are balanced for turning about the axis A to vary the convexity of the portion of the roll face engaging a travelling sheet 30 (See FIGURE 2).

A pair of counterweight disks 26 are mounted in angularly-adjustable relationship on one of the stub shafts 24, being secured in place by a screw 28. Each of the counterweights may be eccentric, so that the amount of counterweight imbalance, and its angular position relative to the axle 18, may be adjusted independently. The sheet 30 passes over the roll in the direction shown by the arrow in FIGURE 2, and a certain amount of torque is required to turn the roll continuously on its axle; the counterweights 26 balance this torque. When handling very stretchy sheet materials, or when a very low tension is applied to the sheet, lack of counterweighting might result in the axle 18 turning continuously about the axis A, which would render the device ineffective. In other situations, the torque required to turn the roll may tend to rotate its concave face into the sheet, making the edges of the web tighter than the center. More or less counterweighting should be applied and centered angularly, as necessary to offset this tendency.

The stub shafts 24 are rotatably supported in a pair of self-aligning bearings 32, which permit the roll and axle to tilt endwise. The inner race of one of these bearings is loose on the corresponding stub shaft 24, to permit the relative axial movement entailed in the tilting motion. The housings of the bearings are secured to a pair of pivot arms 34, which have stiffening webs 36. The arms terminate in pivotal axles 38, which are rotatably supported in pillow blocks 40 to define an offset axis D common to both arms 34; the axis D is offset from, and normally parallel to, the axis A. The entire structure is supported upon a suitable machine framework 42, as may be adapted to the particular installation. A pair of stop screws 43 having lock nuts 45 are threaded through the framework, each to limit the angular movement of one of the arms 34.

In a preferred orientation of the apparatus, the arms 34 extend with a horizontal component of direction as shown in FIGURE 2, so that the weight of the roll and the arms biases it downwardly into the sheet 30, passing beneath the roll. It is generally desirable to counterbalance this weight at least partially, and this is accomplished in the illustrated embodiment by means of pairs of tension springs 44, attached by threaded fasteners 46 to the arms 34, and by threaded hooks 48 to angle brackets 50 aflixed to the mounting structure. The degree of pressure of the roll against the sheet is adjustable by means of nuts 52. If the sheet is passed over the top or sides of the roll, the springs are arranged to bias the roll into the sheet. It will be apparent that other yieldable biasing means can be used in place of springs, such as counterweights, pneumatic cylinders, and the like.

The sheet 30 is guided by appropriate means over the roll 10, illustrated in FIGURES 3-6 as a straight idler roll 54 and a winding roll 56. These means are arranged to give the sheet a suitable wrap angle about the periphery of the roll 10. As is well understood in the art, the most desirable wrap angle depends upon thet amount of lateral spreading action or wrinkle removal required. The tension of the counterbalancing springs 44 may be adjusted by the nuts 52 to apply the amount of unbalanced roll, axle, and arm weight to the sheet necessary to de fiect the sheet to the desired wrap angle, in the existing state of sheet tension. It should be noted that the convex face of the roll normally faces downstream in the direction of sheet travel, so that it tends to spread the sheet laterally and remove wrinkles.

The operation of the device is best illustrated in FIG- URES 3-6. A normal condition is shown in FIGURE 3, the edges E and center C of the sheet being equally taut, with no appreciable slack. The convex face of the roll faces downstream, and the axis A is parallel to the rolls 54 and 56 and the axis D. Therefore there is equal contact of the roll with the center and both edges of the sheet. It should be noted in FIGURE 1 that the axis A interests the axis B at points falling between the center and either end of the roll; therefore, opposite moments are applied upwardly by the sheet against the middle of the roll and its ends, acting about the axis A on which the axles 24 are aligned.

In the event that the central portion of the sheet becomes slack while the edges remain taut, the edge portions will exert an unbalanced moment upwardly on the end portions of the roll 10, acting about the axis A as a center. This rotates the axle of the roll 10, which assumes a position as shown at 10A in FIGURE 4, turning its convex face into the sheet, and thus pressing the middle of the roll further into the center C while partially withdrawing the ends of the roll from the edges E. The angular movement ceases when uniform contact is made across the width of the roll, and the slack in the center is correspondingly eliminated.

Should the edges of the sheet become slacker than the center, an opposite rotation of the roll axle arises from the unbalanced moment applied upwardly by the sheet against the central part of the roll, and the roll assumes a position 108 as shown in FIGURE 5. The convex face of the roll tilts up and out of the sheet, relieving the pressure on the center C while increasing the tautness of the edges E, until a uniform degree of contact is obtained and the slack edges are eliminated.

In each of the ofregoing hypothetical situations, the axis A of the roll remains parallel to the axis D, since the opposite edges of the sheet are assumed to be equally taut or slack. However, in the event that one of the sheet edges becomes slack relative to the other, the unequal reaction of the sheet tilts the roll endwise, with corresponding opposite pivotal movements of the two stub axes 24 about the axis D, as illustrated at 24N and 24F in FIGURE 6. The axis A is tilted and no longer parallel to the axis D. It is assumed in the drawing that the near edge EN has become slack while the far edge EF remained taut. The tautness of the center C is unchanged by the corrective action, but -EN and EF are equalized to remove the slack from EN. It follows that the tension in EF is correspondingly reduced, but suificient initial sheet tension will prevent it actually becoming slack.

In a sense, the roll curvature provides lever arms lying on opposite sides of the rectilinear axis. A pair of first lever arms is provided by the curved end portions of the roll which lie on one side of the axis. A second lever arm is provided by the curved center portions of the roll which lie on the other side of the axis. A thrust of the Web edges upwardly (as viewed in FIG. 4) tends to act against the first lever arms to rotate the roll clockwise about the axis. A thrust upwardly of the center portion of the web acts against the second lever arm upwardly to rotate the roll counterclockwise about the axis (see FIG. 5).

The more the tension at the edges, the greater the upward thrust of the edges (as compared to the thrust of the web center) and clockwise rotation of the roll about the axis. The greater the tension at the center, the greater the thrust at the center (as compared to the thrust at the edges) and counterclockwise rotation of the roll.

In practice, various combinations of the illustrated slack conditions occur; it will be understood that the angular movement and the endwise tilting movement of the roll axle are independently operative to correct any such variations.

In an alternative embodiment, the arms 34 are replaced by other support means which permit endwise tilting movement of the roll and its axle, ,independent of angular movement of the axle about the axis A. For example, the stub shafts 24 may be slidably received in slots formed in a supporting frame and extending with a component of direction normal to the surface of the sheet. The axles would preferably be biased into the sheet by its own weight and/or by means such as springs, pneumatic cylinders, or counterweights, or the like, which may be adjustable. It will be understood that this modified embodiment operates in substantially the same fashion as the illustrated device.

Referring now to FIGS. 7 and 8 for an illustration of an alternative embodiment, at each end of the apparatus is provided a slotted upright plate 70, the slot 72 therein being of sufficient width to receive in sliding manner the stub shafts 24 at each end of the roll which define the axis A. The roll structure is the same as described for the first embodiment, the stub shafts being fastened to the clamping blocks 20, and each end of the axle 18 is held in the aforesaid angularly-adjusted relation within the split clamping blocks 20 by means of the set screws 22, all as described above. Thus, each end of the rectilinear axis defined by the stub shafts 24 is free to move up and downwardly in slots 72 with respect to the sheet traversing the roll independently of the other end of the roll, and the roll itself is adapted to turn about the axis A.

While I have described a preferred embodiment of my invention by way of illustration, it will be apparent to those skilled in the art that additional changes and modifications may be made therein without departing from the true spirit and scope of the invention. For example, the counterweight disks 26 might be omitted, and the axis A ofiset from the center of gravity C.G. of the roll enough to counterbalance the axle 18 against rotating or turning with the roll 10.

What I claim is:

1. A slack eliminating device for use in a sheet-feeding apparatus, comprising, in combination:

a curved roll having longitudinally-curved axle means and rotatable about a curved axis of said axle means for engagement with a sheet travelling under longitudinal tension and partially wrapped about the surface of said roll;

first support means at each end of the roll constructed and arranged for supporting the ends of said axle means for angular displacement about a rectilinear axis parallel to a straight line connecting the ends of said axle means, said first support means and said roll applying turning moments at least partially by gravity about said rectilinear axis to said axle means;

second support means mounting each of said first support means for independent motion to provide for endwise tilting movement of the roll;

said roll being adapted to lie across the width of said sheet with said end portions contacting edge portions of the sheet and said center portion contacting the center portion of the sheet;

said rectilinear axis being positioned relative to the sheet and said axle means so that tension evenly distributed between the center and edges of the sheet applies reaction moments of tension about said rectilinear axis to said roll which balance said turning moments to hold said axle means in neutral equilibrium; tension unevenly distributed as between central and edge portions of the sheet applies reaction moments of tension about said rectilinear axis which do not balance said turning moments, thereby displacing said axle means angularly about said rectilinear axis so as to secure equal contact of said roll with said central and edge portions; and tension unevenly distributed as between op 6 posite edge portions of the sheet applies unbalanced reaction moments of tension acting on the opposite end portions of said roll about an axis normal to said rectilinear axis to tilt said axle means endwise so as to secure equal contact of said roll with said edge portions.

2. A slack eliminating device as recited in claim 1, together with means constructed and arranged for biasing said axle means to apply a desired level of pressure of said roll against the travelling sheet.

3. A device as recited in claim 2 in which said biasing means are adjustable to vary the pressure applied by said roll to the sheet.

4. A slack eliminating device as recited in claim 1, together with means constructed and arranged to pass the travelling sheet to and from said roll and to engage said sheet with said roll about a predetermined normal wrap angle dependent on the position of said roll.

5. A device as recited in claim 4; together with means adjustably biasing said roll into the travelling sheet for adjustment of the wrap angle.

6. A slack eliminating device as recited in claim 1; in which said axle means comprise a longitudinally-curved central axle and a pair of stub shafts one affixed to each end of said axle in eccentric relation, said stub shafts being aligned with one another and rotatably mounted in said support means to define said rectilinear axis.

7. A slack eliminating device as recited in claim 1, in

.which said rectilinear axis intersects said curved axis at two points each one spaced between the longitudinal center and an end of said roll, whereby the reaction moment of the sheet against said roll intermediate said two points acts about said rectilinear axis in a sense opposite to the reaction moments of the sheet against said roll between said points and the corresponding ends of the roll.

8. A slack eliminating device as recited in claim 1, in which said second support means comprise arm means supporting opposite ends of said axle .means for independent pivotal movement about an axis offset from said rectilinear axis and extending parallel thereto in a normal untilted position of said roll.

9. A slack eliminating device as recited in claim 1, in which said first support means include counterweight means for applying a turning moment about said rectilinear axis.

References Cited UNITED STATES PATENTS 2,674,776 4/ 1954 Robertson 26-63 3,107,036 10/1963 Richards et al. 3,171,579 3/1965 Robertson 226-23 3,254,818 6/1966 Jacobsen 226- XR 3,300,114 1/1967 Jacobsen 226-480 3,330,456 7/ 1967 Umstott 26-63 XR FOREIGN PATENTS 209,292 5/ 1960 Austria.

ROBERT R. MACKEY, Primary Examiner US. Cl. X.R. 226-21, 180 

